I have been trying to put together a video tutorial because I think it is easier to follow, but I am pretty horrible at it so here is a photo tutorial instead
This is just a basic skill, but it is useful! Making cords this way can be used for spaghetti straps, button loops, or as a ribbon, which is what I made mine for! And if you don't want to use ribbon for the ribbon bustle skirt tutorial I am working on, this cord is a perfect substitute. I like to use cords because you can make it out of matching fabric, and it is not as slippery as ribbon.
First, cut your fabric into strips four times wider than your finished cord. I wanted 1/4" wide cords, so I cut 1" wide strips. Fold in half and stitch at your cord width (1/4" for me)
I used white thread so you can see easily. Obviously you want to use matching thread!
Make a snip from the FOLDED edge to, but not through, your stitching line
Put a bobby pin in the little loop you just made
Thread the bobby pin into the body of the cord. Start feeding the bobby pin through and the cord will fold in on itself. Don't try to turn too much at once or it will just bunch up! Start small. Once you have a good few inches turned, it becomes much easier! I find that if the end gets a little bit bunchy, especially in the beginning, twisting and rolling it between your fingers helps.
I showed the twisting portion in the video I recorded but I can't seem to make a good video edit
If you need more explanation, please let me know!